This application claims the benefit of Japanese Application No. 11-017846, filed in Japan on Jan. 27, 1999.
1. Field of the Invention
The present invention relates to an inverse telecine converting device and an inverse telecine converting method for converting quasi television motion pictures produced from frame pictures of a cinema into frame pictures of the original cinema.
2. Description of the Related Art
With respect to television motion pictures, picture information of 30 frames per second (hereinafter referred to as xe2x80x9cframe picture informationxe2x80x9d is time-sequentially displayed on a screen. As shown in FIG. 1, frame picture information 80 is constructed by combining top field picture information 81 and bottom field picture information 82 and then scanning both portions of the field picture information.
A conversion method shown in FIG. 2 (hereinafter referred to as xe2x80x9ctelecine conversionxe2x80x9d) has been hitherto utilized to produce video motion pictures for TV from a cinema film (24 frames per second) because the number of frames per second is different between the cinema and the TV formats. According to the conventional telecine conversion method, the frame picture information of a cinema (movie) is replaced as top field picture information (at the upper stage of the video field of FIG. 2) or bottom field picture information (at the lower stage of the video field of FIG. 2).
Through this telecine conversion, one field picture information piece is inserted as repetitive field picture information every five field picture information pieces. There are two cases for the insertion of the repetitive field picture information. In one case, the just-previous top field picture information (the second preceding field picture information) is set as top field image information corresponding to the repetitive field picture information concerned. In the other case, the just-previous bottom field picture information (the second preceding field picture) is set as bottom field image information corresponding to the repetitive field picture information concerned. In the following description, the television motion picture information thus produced from the cinema film is referred to as xe2x80x9cquasi television motion picture informationxe2x80x9d.
Recently, DVD (Digital Versatile Disk) has been rapidly developed and now being popularized in the market. The propagation of DVD has promoted the production of motion picture software (video contents) for DVD from conventional quasi television motion picture information. When motion picture software (video content) for DVD is produced from conventional quasi television motion picture information, it is indispensable to delete repetitive field picture information in the quasi television motion picture information and return the quasi television motion picture information to picture information of 24 frames per second (hereinafter referred to as xe2x80x9cinverse telecine conversionxe2x80x9d).
The importance of deleting the repetitive field information is two-fold. First, the picture information is subjected to compression (encoding) processing for DVDs. In this case, the compression efficiency is increased by returning quasi television motion picture information (30 frames per second) containing repetitive field picture information to original cinema motion picture information (24 frames per second) containing no redundant information and then compressing the original cinema motion picture information, as compared to directly compressing the quasi television motion picture information. Here, the image quality also is better with the repetitive field information removed for a specific amount of data. Second, when picture information is reproduced in a DVD reproducing device (player) while advancing frames, the frame advance of a cinema film can be directly implemented.
FIG. 3 is a conceptual diagram showing inverse telecine conversion in the conventional inverse telecine converting device.
As shown in FIG. 3, quasi television motion picture information (i.e., video frames at 30 frames per second) obtained from a telecine converted cinema film processing is input to an inverse telecine conversion device. Repetitive field picture information contained in the quasi television motion picture information is deleted as indicated by the dotted-line frame in FIG. 3, thereby converting the quasi television motion picture information to the picture information of a reproduced original movie film of 24 frames per second.
At the same time, control flags which are needed to re-convert the picture information of 24 frames per second to television picture information of 30 frames per second, are generated and added to the frames of the picture information of the original movie film thus reproduced. In FIG. 3, a control flag TFF controls to give priority to the top field picture information in the frame provided with the control flag TFF. A control flag BFF controls to give priority to the bottom field picture information in the frame provided with the control flag BFF. A control flag RFF controls to set the first field picture information in the frame concerned to the repetitive field picture information.
Next, the principle of conventional inverse telecine conversion will be described.
As described above, the insertion period and the insertion position of the repetitive field picture information pieces which are inserted through the conventional telecine conversion are determined in advance. A method of deleting the field picture information pieces located at predetermined positions every five fields using the above fact (hereinafter referred to as xe2x80x9cfixed-period field deletion methodxe2x80x9d) is considered to be the simplest method. In the case of cinema, a cinema (movie) is normally composed of a set of plural film rolls. In this case, the picture information of each film roll is converted to television motion picture information. Then, the television motion picture information corresponding to the film rolls are joined together and edited to obtain one video tape. However, the top fields or bottom fields are usually displaced between the front and back sides at the place where the two portions are joined with respect to the joint places. Therefore, the period of the repetitive field picture information is deviated from the fixed period. Accordingly, if the fixed-period field deletion method is applied carelessly, originally-needed picture information that is not repetitive field picture information may be deleted.
FIG. 4 shows an inverse telecine converting method that has been conventionally used to solve the above problem. According to this method, the correlation between the pixel values of timely-adjacent top field picture information pieces and the correlation between the pixel values of timely-adjacent bottom field picture information pieces are checked over several frames of quasi television motion picture information obtained through the telecine conversion processing. Then, one of two field picture information pieces which are judged to be highly correlated with each other is regarded as repetitive field picture information and deleted.
In the conventional inverse telecine converting device shown in FIG. 4, however, in a case of pictures having a lot of noise or in a case of pictures of a scene having little motion, any field picture information piece will have high correlation in pixel value with another field picture information piece. Thus, it is difficult to identify which field picture information piece is repetitive field picture information.
Accordingly, the present invention is directed to a inverse telecine converting device and inverse telecine converting method that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an inverse telecine converting device and an inverse telecine converting method that can identify repetitive field picture information for even pictures containing a lot of noise and pictures of a scene having little motion.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, an inverse telecine converting device converts quasi-television motion picture information back to original cinema motion picture information, wherein the quasi-television motion picture information has been obtained by quasi-converting the original cinema motion picture information. The inverse telecine converting device includes means for inputting the quasi-television motion picture information including field picture information pieces time-sequentially arranged at a rate of N frames per second (N being a natural number), each frame of the quasi-television motion picture information including top and bottom field picture information pieces such that one of every P field picture information pieces (with P being a natural number) of the quasi-television motion picture information is a repetitive field picture information piece; means for producing judgment frame picture information pieces on the basis of timely-adjacent field picture information pieces of the quasi television motion picture; means for determining the structure of each judgment frame as being one of a frame structure and a field structure; means for identifying the repetitive field picture information pieces on the basis of the determined structures corresponding to timely-adjacent judgment frame picture information pieces; and means for outputting the original cinema motion picture information arranged at a rate of M frames per second (with M being a natural number).
In another aspect, an inverse telecine converting method converts quasi-television motion picture information back to original cinema motion picture information, wherein the quasi-television motion picture information has been obtained by quasi-converting the original cinema motion picture information. The inverse telecine converting method includes inputting the quasi-television motion picture information including field picture information pieces time-sequentially arranged at a rate of N frames per second (with N being a natural number), each frame of the quasi-television motion picture information including top and bottom field picture information pieces such that one of every P field picture information pieces (with P being a natural number) of the quasi-television motion picture information is a repetitive field picture information piece; producing judgment frames on the basis of timely-adjacent field picture information pieces of the quasi television motion picture; determining the structure of each judgment frame as being one of a frame structure and a field structure; identifying the repetitive field picture information pieces on the basis of the determined structures corresponding to timely-adjacent judgment frame picture information pieces; and outputting the original cinema motion picture information arranged at a rate of M frames per second (with M being a natural number).
In another aspect, an inverse telecine converting device for converts quasi-television motion picture information back to original cinema motion picture information, wherein the quasi-television motion picture information has been obtained by quasi-converting the original cinema motion picture information. The inverse telecine converting device includes first, second, and third field delays to receive a series of field picture information pieces from an input; first, second, and third block generators to combine timely-adjacent field picture information pieces received from the input and the first, second and third field delays to produce a series of judgment frame picture information pieces, each of the judgment frame picture information pieces including two timely-adjacent information pieces; a plurality of orthogonal transformers to subject each judgment frame to orthogonal transformation and to obtain a high-order coefficient of a frequency area on the basis of pixel values in the vertical direction for each judgment frame; and a comparator to compare each high-order coefficient and to determine whether each respective judgment frame picture information piece has a frame structure or a field structure.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.